DFW AIRPORT, TX, USA
N710AA
BOEING 727-200
ACFT RECEIVED MINOR DAMAGE WHEN THE PLT EXECUTED AN EMERGENCY GEAR UP LANDING FOLLOWING THE FAILURE OF THE MLG TO EXTEND USING NORMAL, ABNORMAL, AND MANUAL PROCEDURES. ACFT WAS LANDED WITH THE NLG EXTENDED AND THE MAINS RETRACTED. INVESTIGATION REVEALED THAT THE LEFT MLG DOOR ACTUATOR PIVOT TRUNNION UPPER SHAFT HAD FAILED AS A RESULT OF A FATIGUE FRACTURE. FOLLOWING THE FRACTURE, THE SEPARATED SHAFT HAD BECOME JAMMED BETWEEN THE TRUNNION AND THE ACTUATOR CLEVIS WHICH PREVENTED THE MANUAL DOOR UNLOCK MECHANISM FROM RELEASING. A REVIEW OF THE SERVICE DIFFICULTY HISTORY OF THE FAILED PART INDICATED THAT SEVERAL SIMILAR FAILURES HAD OCCURRED ON MANUFACTURED PARTS AND THAT A REDESIGNED PART WAS AVAILABLE FOR REPLACEMENT. THE OPERATOR HAD COMPLIED WITH ALL OF THE REQUIRED INSP'S.
FATIGUE FAILURE OF THE LEFT MAIN LANDING GEAR DOOR ACTUATOR PIVOT TRUNNION SHAFT WHICH SUBSEQUENTLY BECAME LODGED IN THE ACTUATOR CLEVIS PREVENTING THE DOOR UNLOCK MECHANISM FROM ACTUATING DURING GEAR EXTENSION.
Source: NTSB Aviation Accident Database
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